A filtration system of such type has been proposed in the U.S. Pat. No. 6,863,868 B1 and the filter candles used are catalytic filter candles such that the filtration system may be used for hot gas filtration.
Differently structured filter systems for cleaning flue gases are known from EP 0 600 440 A2 wherein a barrier filter module is used together with a separate catalyst module. The raw gas is first passed through the barrier filter module and then passed through the catalyst module.
Both types of catalytic filter systems are useful in flue gas treatment since they provide at the same time particle separation and a catalytic gas phase reaction in one unit.
However, the problem of such combined particle separation/catalytic gas phase reaction devices is that in cases where high catalytic conversion rates are required and have to be guaranteed for high inlet concentrations, the face velocity of the raw gas has to be reduced in order to increase the residence time of the gas for the catalytic reaction in the catalytic element. This leads to an increase of the number of filter elements in order to meet the required throughput and correspondingly to an increase of the size of the filter system.
In order to cope with the challenge of the particle load of the raw gas, i.e., the filtration action, such increase in size of the filter system typically would not be necessary.